The present invention relates to an improvement in a structure for accurately connecting a connection pattern provided on a leadless chip carrier (LCC) to that provided on a receiving surface using a connector in place of solder.
An LCC is usually provided with a connection pattern which is to be connected to that provided on a receiving surface, which is usually a printed circuit board, with the intermediary of a connector. Such connection may be implemented with a structure in which a frame with a through bore is mounted on the receiving surface to surround the connection pattern on the receiving surface. The LCC is loosely received in the bore of the frame through a conductor connector, while a cover which has a pressing tongue at the center thereof presses the LCC from above to retain it in a predetermined position.
Generally, since the dimensions of the outer contour of LCCs coming out of a production line very substantially, the bore of the frame adapted to position the pattern on an LCC relative to the pattern on a receiving surface needs to be sized large enough to accommodate a product, or LCC, having the largest presumable dimensions. This, however, brings about a problem that when a relatively small LCC is placed in the relatively large bore of the frame, it is apt to move laterally or angularly inside the bore so that predetermined contacts of the pattern on the LCC fail to attain accurate contact with those of the pattern on the receiving surface, resulting in an imcomplete connection.
Furthermore, the dimensional variations of LCCs extends over to the thickness for production reasons. Should such thicknesswise variations be left unabsorbed, the connector would fail to be constantly biased by an adequate force, constituting another cause of incomplete connection. In this respect, as previously stated, the cover is provided with a pressing tongue which presses the LCC from above in order to absorb the thicknesswise variations. However, it is impracticable to absorb the entire thicknesswise variations by means of the pressing tongue only, unless the tongue is provided with greater dimensions or a stronger biasing force. Such not only adds to the overall size and weight of the resulting package but also requires an LCC to be carefully designed in due consideration of its resistivity to externally derived pressures.
Meanwhile, when it is desired to replace the LCC which is fully received in the bore of the frame as previously described, the LCC has to be removed by turning the whole package and receiving surface upside down so that the LCC may drop out of the frame. It follows that where such a substrate is installed in an apparatus, the LCC cannot be removed unless the whole apparatus is turned upside down.